Amblyopia & its management by sivateja challa
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Transcript of Amblyopia & its management by sivateja challa
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AMBLYOPIA
SIVA TEJA CHALLA
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AMBLYOPIA• DEFINITION• EPIDEMIOLOGY• PATHOPHYSIOLOGY• CLASSIFICATION AND TYPES• CLINICAL FEATURES AND DIAGNOSIS• TREATMENT MODALITIES.
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DEFINITION• U/L or less commonly B/L reduction in
BCVA that cannot be attributed directly to the affect of any structural abnormality of the eye or the posterior visual pathways
• M.C.C of dec vision in childhood• For practical purposes defined as atleast 2
snellen line difference b/w two eyes
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EPIDEMIOLOGY
• In developed countries 1-5% of the population
• In india affects 1-4% of children• Goel et al. found the incidence to be 0.7% in
rural schools than in urban schools 0.5%• Onset is birth to 7 yrs of age• SE Factors does not significantly influence
the age of presentation of amblyopia• Earlier the onset greater the defecit
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• Four times more frequent in premature children
• Six times more frequent in children with delayed mile stones
• Smoking and use of dugs and alcohol during pregnancy have been asso with risk of amblyopia
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PATHOPHYSIOLOGY
Amblyogenic factors
Role of retina
Active cortical inhibition
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Amblyogenic factorsVISUAL
DEPRIVATION
monocularSeen in strabismic ,
anisometropic, stimulus deprivation
amblyopiaBinocular
Seen in bilateral cataract, ametropia and bilateral high refractive errors
LIGHT DEPRIVATION.Usually seen in children with
unilateral or bilateral complete cataracts.
ABNORMAL BINOCULAR
INTERACTION-produces profound amblyopia due to
competition amblyopia.
-seen in strabismic, anisometropic and unilateral stimulus
deprivation amblyopia.
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RETINA IN THE DEVELOPMENT OF AMBLYOPIA
• Decreased sensitivity of foveal cones in amblyopia
• The reduced input from rods and cones in the affected eye causes certain neurophysiologic changes, transmitted to the CNS which triggers amblyopia.
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ACTIVE CORTICAL INHIBITION1) A developmental defect of spatial visual processing occurring in the visual pathway.
2) Poor transmission from the fovea, optic nerve to the Striate Cortex of the affected eye.
3) LGB & Striate cortex develop abnormally.
4) Ganglion cells in foveal area are affected; Shrinkage of LGB Nucleus & Striate cortical fibres in the amblyopic eye.
5) Loss of binocularly driven cells in LGB & Striate Cortex
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CLASSIFICATION & TYPES• Strabismic amblyopia.• Stimulus deprivation or amblyopia of disuse.• Anisometropic amblyopia.• Meridional amblyopia.• Isoametropic amblyopia .• Amblyopia secondary to nystagmus.• Idiopathic amblyopia.• organic amblyopia.
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Amblyopia
‘Organic Amblyopia’
Irreversible
Structural abnormal Mac scar, Optic
atrophy
‘Functional Amblyopia’
Reversible(when t/t early)
•Strabismic•Anisometric•Visual Deprivation
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STRABISMIC AMBLYOPIA• M/C form of amblyopia• A.K.A amblyopia of arrest• Seen in unilateral constant squint who
strongly favour one eye for fixation.• cortical suppression from deviating eye
thought to be due to inhibitory interactions from neurons carrying non fusable images which cause visual confusion
• Esotropia more likely to develop amblyopia as compared to exotropia
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• Does not develop in alternating or intermittent strabismus as there are periods of normal binocular interaction that preserve the integrity of visual system
• Severity of amblyopia does not correlate with angle of strabismus
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STIMULUS DEPRIVATION AMBLYOPIA
• Amblyopia ex anopsia disuse amblyopia.• Least common but most damaging.• Cause when the visual axis is obstructed.• Monocular congenital or traumatic
cataract, complete ptosis, corneal opacity & prolonged patching of the normal eye for treatment of amblyopia.
• Less than 6 yrs – severe amblyopia.• After 6 yrs – less harmful .
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• Visual loss resulting from unilateral deprivation is worse than that produced by bilateral deprivation of similar degree
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ANISOMETROPIC AMBLYOPIA
• 2nd m.c.c of amblyopia• develops when unequal refractive errors in
the 2 eyes causes the image on 1 retina to be chronically defocused.
• Most patients with anisometropic amblyopia have straight eyes and appear “normal,” so the only way to identify these patients is through vision screening.
• Hypermetopic anisometropia is more amblyogenic than myopic anisometropia
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• The amount of anisometropia that can induce amblyopia varies according to the type of refractive error
• Amount of anisometropia Hypermetropia > 2D
Myopia > 4D
Astigmatism > 1.25D
However unilateral high hyperopia or myopia (>6D) causes severe amblyopia
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MERIDIONAL AMBLYOPIA• Resolution of eye is reduced in selective
meridians as a result of un corrected astigmatism
• Cylinder >1.5D is comsidered amblyogenic• Doesn’t develop until first year of age
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ISOMETROPIC AMBLYOPIA• Bilateral amblyopia occurring in children
with bilateral uncorrected high refractive error.
Hyperopia > +5 D.
Myopia > -10 D.
astigmatism > 2D
Mechanism – effect of blurred retinal images alone
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AMBLYOPIA SECONDARY TO NYSTAGMUS
• Difficult to establish ascertain whether nystagmus is the cause or effect of amblyopia
• Bilateral
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IDIOPATHIC AMBLYOPIA
• Occurring in apparently normal patients with a negative history of strabismus & in the absence of other amblyogenic factors.
• Mech- foveal suppression of amblyogenic eye d/t transient amblyogenic factor during infancy
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CLINICAL CHARACTERISTICS• Decreased visual acuity• Decreased stereoacity• Fixation reflex• Crowding phenomenon• Effect of neutral density filter• Contrast sensitivity • Fixation pattern
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VISUAL ACUITY• Two line difference between amblyopic and normal
eye• For B/L amblyopia the VA should be less than
20/40 in each eye• But in children there will be difficulty in assesing
VA
Infants-fixation preference
preverbal children-preferential looking test,OKN test,VEP
2-3 yrs- E charts,pictoral charts
>3 yrs-snellens charts,HOTV charts
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PREFERENTIAL LOOKING TEST
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STEREOACUITY• Presence of amblyopia can be detected by
defective performance on various stereograms
• Two pencil test is a clinically useful test and can be applied even when VA recording is unreliable or not possible
• Can also be easured by titmus fly test,random dot stereogram
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FIXATION REFLEX• useful tool to assess VA in children <5yrs of age• Central steady and maintained (CSM) fixation
implies good VA
Affixation <3/60
unsteady fixation 3/60 to 6/60
Central but not maintained 6/60 to 6/18
Central but strong preference for other eye 6/18 to 6/9
Alternate fixation 6/6
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CROWDING PHENOMENON• Amblyopia pts exhibit better VA for single
optotypes than for letters placed in a row• Although not specific for amblyopia,it may be
pronounced in amblyopic eye compared to better eye
• Single line acuity improves more than line acuity during treatment
• So it is important to record both single letter and line visual acuity every time as it is prognostic indicator
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• Vision testing with single optotypes is likely to over estimate VA in pts with amblyopia
• More accurate assesment of mono ocular VA is obtained with the presentation of line of optotypes or single optotype with crowding bars that surround the optotype being identified
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NEUTRAL DENSITY FILTER• A neutral density filter reduces overall luminance
without inducing a color change.• Decreased luminance of the visual target results in
diminished central acuity in normal eyes.• Decreased illumination of visual targets has less of
an effect on amblyopic eyes because they are not using central acuity
• It was found that neutral filters profoundly reduce vision in eyes with organic amblyopia whereas vision of eyes with functional amblyopia was not reduced and occasionally even slightly improved.
• Hence it can be used to differentiate the two.
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CONTRAST SENSITIVITY• Reduction in contrast
sensitivity more for higher frequencies
• Improves during amblyopia therapy and useful to monitor the progress
• Contrast threshold becomes normal in strabismic amblyopia when luminance levels were reduced, while the deficit persists in anisometropic amblyopia
pelli robson contrast sensitivity chart
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FIXATION PATTERN• Bangerter’s classification of fixation patterns in
amblyopia
I. Central fixation
II. Eccentric fixation (nonfoveolar)- common type
III. No fixation• Patients with eccentric fixation appear to be
looking to the side,not directly at the fixation target. They have poor smooth pursuits,so they do not accurately follow a moving target.
• Can be tested in old coperative children by visuoscope
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OTHER FEATURES• VEP Reduction in amplitude and slightly
prolonged latency• Afferent pupillary defect may be seen• Normalisation of VA in dim light
occasionally• Occasionally latent nystagmus
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CLINICAL EVALUATION & DIAGNOSIS
• Thorough clinical history• Binocular red reflex test• Binocularity/stereo acuity testig• Evaluation of visual acuity and fixation pattern• Binocular alingnment and ocular motility• External examination• Pupillary examinaion• Thorough ocular examination including fundus examination.• Cycloplegic retinoscopy/Refraction• Neutral density filter and testing for crowding phenomenon.
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TREATMENT MODALITIESTreatment of amblyopia involves following steps:-
1) eliminate any obstacles to vision , such as cataract.
2) correct any significant error.
3) force use of the poorer eye by limiting use of the better eye.
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• Refractive correction• Occlusion therapy• Penalisation• Drug therapy• Pleoptics • Cam stimulator• Surgery to treat the cause of amblyopia
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CATARACT REMOVAL
• Removal of congenital lens opacity- first 4 -6 week of life.
• If symmetrical b/l cases- interval b/w 1st & 2nd eye should not be not more than 1-2 weeks.
• Developing severe traumatic cataract in children less than 6 yrs removed within few weeks of injury.
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REFRACTIVE ERROR CORRECTION• Improves VA in 25-33% of patients with anisometropic
amblyopia and also in strabismic amblyopia• Cycloplegic refraction followed by adequate optical
correction• ATS 5 concluded that amblyopia improved with
optical correction in 77% and resolved in 27%• Chen et al (AJO 2007) concluded that penalisation
and occlusion is required only if the child doesn’t improve with glasses for four months
• In general eye glasses are well tolerated by children especially when there is improvement in visual function
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OCCLUSION THERAPY• Occlusion of the sound eye is the most effective
treatment for amblyopia treatment• When fixation is central, simple & effective.• When fixation is eccentric, <7yrs central fixation
will be recovered.• Older the child harder to regain central fixation.• Success rate 30-92%• MOAprevent fixating eye taking part in act of
vision and removes inhibitory stimulus that arises from stimulation from fixating eye
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Types of occlusion• Total or partial• Conventional or inverse• Full time or part time
• Patching is most commonly prescribed,however contravercy exists concerning how much treatment is necessary
• Most data on response according to daily dosage of patching are retrospective and uncontrolled
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TOTAL VS PARTIAL OCCLUSION
total
partial
•All light is prevented from entering eye.•Employed in amblyopic eyes with acuity less than 6/24•Occlusion using elastoplast, gauze pad, tape, doynes rubber occluder.
•Does not cut off the total light entering eye•Degrades the vision of normal eye such that amblyopic eye gets better vision and preference•Occlusion using cellophane, transparent nail polish, or a higher plus lens.
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CONVENTIONAL VS INVERSE OCCLUSION Conventional Inverse
•Occlusion of sound eye
•Occlusion of amblyopic eye so that eccentric fixation becomes less fixed
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FULL TIME VS PART TIME Full time Part time
Removed only while going to bed at night
Short time each day during close work or watching television.
Choice of initial Rx In relapses after Rx and also for maintanence
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Types of occluders• Adhesive skin patches made of micropore• Commercially available opticlude• Spectacle occluder• Contact lens occluder
OPAQUE CONTACT LENS
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• Patches • Micropore tape with soft tissue paper
• Spectacle patch / frost glass • Doyne’s occluder
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Paediatric eye disease investigator group(PEDIG) has conducted several amblyopia treatment trials (amblyopia treatment study or ATS) over the past several years. Results have shown that• Spectacles alone are powerful treatment for
amblyopia; patching is superior to spectacles• Initiating fewer hours of prescribed patching
seems to be as effective as traditional treatment• Patching is effective in older children particularly
if they have not been treated earlier• Atropine is as effective as patching• Weekend atropine is as effective as daily atropine
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How much patching??The amblyopia treatment study have helped to define the role of full time patching vs part time patching• In patients aged 3-7 years with severe
amblyopia (VA B/W 6/30 to 6/120) full time patching produced similar effect to that of six hours patching per day
• In patients aged 3-7 years with moderate amblyopia (VA better than 6/30) 2 hours patching produced similar effect to that of six hours patching per day
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Treatment of amblyopia in 7-17 yrs• For 7-13 yrs age group 2-6 hours of
patching can improve VA only if previously treated
• For 13-17 yrs age group 2-6 hous of patching improved VA even if not treated previously
• Long term results from these studies are still pending
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HOW TO GO ABOUT OCCLUSION
• Motivation of child and parents.• Active vision exercises by amblyopic eye like dotting
O’s and encircling E’s in a newspaper, joining dots,reading comics and story books.
• In case of vision improvement, occlusion is continued till amblyopic eye has not only developed equal vision but also equal preference of fixation.
• May take 3-6 months.• If there is no improvement. Then treatment is stopped.
Also other causes to be ruled out.• Maintainence treatment is continued atleast upto 9 yrs
of age with part time occlusion and exercises
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Rx schedule for initial occlusionAge in yrs Period of
occlusion(days)Direct : inverse
Follow up after every
Upto 2 2 :1 15 days
3 3 : 1 15 days
4 4 : 1 1 month
5 5 : 1 1 month
6 & older 6 : 1 1 month
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• Follow up-depending on age,severiy of amblyopia and compliance
• To look for-VA, fixation pattern and occlusion amblyopia
• When to stop occlusion
VA equals in both eyes
alternation of fixation• When VA is stable patching may be
decreased slowly• Because amblyopia recurres in large no. of
patients maintanence therapy or tapering of therapy should be strongly considered.
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Disadvantages of occlusion• Occlusion amblyopia• Non compliance• Psychological distress• Appearance of constant deviation• Allergic skin rash• Diplopia• Cosmetically inacceptable
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Prognostic considerations• Younger the age better the prognosis
• Type of amblyopia myopic anisometropia> hyperopic anisometropia> strabismic amblyopia> stimulus deprivation
• Pretreatment VA
• Type of occlusion
• Type of fixation
• Near exercises
• Patient compliance and parent education• Presence of astigmatism• Method of treatment termination• Previous treatment• Refractive correction
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TREATMENT OF ANISOMETROPIC AMBLYOPIA
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TREATMENT OF STRABISMIC AMBLYOPIA
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PENALISATION• Therapeutic technique performed by
optically defocussing the eye with better vision by using cycloplegia or altering the eye glass lens
INDICATIONS No compliance for occlusion.Mild degrees of amblyopia.Maintainence after occlusion.Anisometropic amblyopia
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• Advantages cheap,better compliance• DisadvantagesS/E of drugs
risk of occlusion amblyopia
systemic absorption• Unless penalisation decreases the VA of
dominant eye below the amblyopic eye this form of treatment is not adviced
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Methods of penalisationa. Near penalization: fixing eye is
atropinized & fully corrected for distance, amblyopic eye is overcorrected with +2 to +3D .
b. Distance penalization : fixing eye is atropinized & overcorrected, amblyopic eye is fully corrected.
c. Total : fixing eye is atropinized & undercorrected by 4 to 5 D, amblyopic eye is fully corrected.
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PLEOPTICS• Involves active stimulation of fovea to
overcome eccentric fixation & improves Va.
• The peripheral retina including the eccentrically fixing area around the fovea is dazzled.
• After lights are turned off, fovea functions better because the surrounding retinal area is in a state of hypofunction
• ONLY INDICATION IS coperative and intelligent child older than 6yrs having eccentric fixation
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ORE PLEOTOPHORE
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CAM STIMULATOR• Slowly rotating high contrast square wave
grating of different spatial frequencies• Principle – rotating gratings provide
specific stimulation for cortical neurons• the visual improvement was found to be
better in emmetropes and hypermetropes than those in strabismus amblyopia
• Not used these days
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PHARMACOLOGICAL THERAPY• LEVADOPA is the only most extensively
studied drug in western and Indian population• Precursor of dopamine known to influence
visual system at retina and cortical level• Advantages
Augments conventional occlusion
Speeds up recovery of visual functions
Improves compliance
Reduces cost and duration of treatment
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• Catecholamine based medical treatment citicholine has been demonstrated to improve VA in amblyopic eyes
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SURGERYBy reducing anisometropia refractive surgeries has reported to• Improve spectacle tolerance• facilitate amblyopia thearpy• Enhance binocular vision
Also used for children who has finished amblyopia therapy and cannot comply with spectacles or contact lens
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Surgical therapy for strabismus generally should occur after amblyopia is reversed. • Disadvantages to surgical therapy prior to
correction of amblyopia include difficulty in telling if amblyopia is present
because there is no longer a strabismus to assess fixation preference and higher potential to being lost to follow-up, as the child cosmetically looks better.
The improved cosmesis gives the parents a false sense of security about the vision improving
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RECURRENCE• Chances are high until child is visually
mature.• Careful monitoring every month upto 1
year, every 2 months upto 2 years and 4- 6 months upto visual maturity is required.
• Maintainence occlusion to be given
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SCREENING• AAO recommends screening by the age of 3 yrs
and thereafter every 2yrs• Includes visual acuity, corneal reflex test,
refraction, fixation preference and stereo acuity• AAP suggests that vision screening should
begin at birth and continue as a part of child regular medical check up
• All new born infants should be screened in nursery with the use of red reflex
• Infants at risk should undergo detailed evaluation
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Severe amblyopia can be eliminated as a public health problem• The goal can be achieved by improvements in public awareness better screening protocols at the level of
primary health care provider full access to medical care for at risk
patients
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THANK YOU